I have a customer with an outside front porch (uncovered) that has a coating of some sort ( she doesn't know what was used initially ); it was probably a poly product.  The porch floor is Saltillo glazed tiles with 1/2 inch grout lines.  I am assuming that I need to strip the current coating and apply a topical coating.  What do you recommend?  I don't work on man made products and rarely outdoor applications, so I need some suggestions.  Thanks in advance for your help.